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List all the Intel-ready apps on your Mac
Authored by: gaoshan on Jan 18, '06 11:40:14AM
what does the
2>/dev/null
portion of this do (I know what /dev/null is for but the 2> I don't know)?

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List all the Intel-ready apps on your Mac
Authored by: fds on Jan 18, '06 02:37:25PM

It redirects error message output, known as stderr.

It's there because many companies ship various files erroneously marked as executables, which would result in lipo outputting an error message for each. This gets rid of them.



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List all the Intel-ready apps on your Mac
Authored by: gidds on Jan 18, '06 03:16:32PM
Indeed.

More detail: in the Unix world, every process gets three standard streams assigned to it: standard input (stdin), standard output (stdout), and standard error (stderr); with file descriptors 0, 1, and 2 resp.

Standard input and output are self-explanatory; they usually go from keyboard and to screen unless you redirect them with > and < or |.

Standard error is another output stream that's used for error messages; it keeps them from getting mixed up with the proper output, and ensures you see errors even if you've redirected stdout. (Another difference is that whereas stdout is buffered for speed, stderr is unbuffered so you get to see your errors immediately.)

It's a little more difficult to redirect stderr: you have to use the more general redirection syntax and precede the > with the file descriptor of the stream to redirect. Remember that stderr's file descriptor is 2? So 2> redirects stderr in the same way that > (or 1>) redirects stdout.

HTH!

---
Andy/

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